Observation of magnetic flux ropes in the Venus ionosphere

摘要: MAGNETIC field measurements made by the Pioneer Venus Orbiter spacecraft reveal a very low average strength within dayside ionosphere of Venus, typically only few nanoteslas, in contrast to fields several tens nanoteslas just outside ionosphere1. Thus, at least range solar zenith angles (65–90°) initially probed orbiter, compressed interplanetary magnetic shocked wind plasma (the magnetosheath) is effectively shielded from currents flowing on ionopause, boundary between and magnetosheath. In addition, pressure ionopause approximately balances ionosphereic thermal pressure2,3. However, this generally low-field region occasionally passes through regions large which can sometimes exceed that observed external ionosphere. These intense, short-lived enhancements are described here interpreted be due passage ‘flux ropes’, bundles twisted lines surrounded ionospheric plasma.